I'm not very familiar with the 'gin no juujika to draculea light novel'. But from the title, it seems to combine several interesting elements. 'Gin' may refer to silver, which could have various symbolic meanings in the story. 'Juujika' usually represents a cross, which might be related to religious or cultural aspects in the novel. And 'draculea' is likely to be related to Dracula or vampire - like creatures. It might be a story about a battle between good and evil, with these elements playing important roles in the plot.
You can try looking for it in local bookstores that specialize in light novels or Japanese literature. Sometimes they have a section dedicated to such niche works.
Well, Manga Rock is just a place where you might find Re:Monster and other manga. But they don't have a specific connection beyond that. Re:Monster is just one of the many manga available on Manga Rock if it's there.
Well, it could be that someone teased it or it faced some sort of obstacle that made it angry. Sometimes, in cartoons, characters get angry for all sorts of random reasons to add drama and fun to the story.
Cute Halloween cartoon drawings often feature big eyes on the characters to make them look endearing. There might be lots of sparkles and glitter for a magical touch. Plus, they might have cute costumes like little witches or vampires with cute hats.